To get back on topic:
When I transition from the first three adds to Twintania, I set up for a Storm's Eye, pop Unchained and Berserk before it lands, Fracture/Internal Release/Infuriate -> BB combo -> half way to BB, Inner Beast just before pacification, then turn off Defiance and finish my BB after it ends.
After this I do:
SE combo -> Fracture -> BB combo -> SE combo -> BB combo
Repeat the above, and either save your damage CD's for the fast Conflags or use them whenever they refresh, depending on whether your group has problems with bursting them down or no. Also, don't forget to use Brutal Swing on CD for the first three phases. It might just be 50 potency, but every bit counts.
EDIT: This is assuming that your MT has built up enough enmity to hold off your BB combo, which really shouldn't be a problem. Keep an eye on the enmity meter for safety measures if you're unsure.